Ultralong C-C bonds in hexaphenylethane derivatives

2008 ◽  
Vol 80 (3) ◽  
pp. 547-553 ◽  
Author(s):  
Takanori Suzuki ◽  
Takashi Takeda ◽  
Hidetoshi Kawai ◽  
Kenshu Fujiwara
Keyword(s):  
Bond Length ◽  
Molecular Design ◽  
Crystal Packing ◽  
Detailed Examination ◽  
Steric Repulsion ◽  
Wide Range ◽  
Rational Molecular Design ◽  
Electron Reduction ◽  
Highly Strained ◽  
Crystal Packing Force

The longer C-C bond than the standard (1.54 Å) is so weakened that it is cleaved easily, as found in the parent hexaphenylethane (HPE). However, the compounds with an ultralong C-C bond (1.75 Å) can be isolated as stable solids when the bond-dissociated species does not undergo any reactions other than bond reformation. This is the central point in designing the highly strained HPEs, which were obtained by two-electron reduction of the corresponding dications. Steric repulsion of "front strain" is the major factor to expand the central C-C bond of HPEs. During the detailed examination of the ultralong C-C bond, the authors discovered the intriguing phenomenon of "expandability": the C-C bond length can be altered over a wide range by applying only a small amount of energy (1 kcal mol-1) supplied by crystal packing force. This observation indicates that the much longer C-C bond than the shortest nonbonded contact (1.80 Å) will be realized under the rational molecular design concept.

scholarly journals Development of ferroelectric nematic fluids with giant-ε dielectricity and nonlinear optical properties

2021 ◽  
Vol 7 (17) ◽  
pp. eabf5047
Author(s):  
Jinxing Li ◽  
Hiroya Nishikawa ◽  
Junichi Kougo ◽  
Junchen Zhou ◽  
Shuqi Dai ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Molecular Design ◽  
Second Harmonic ◽  
Polymeric Materials ◽  
High Dielectric Permittivity ◽  
Wide Range ◽  
Rational Molecular Design ◽  
High Dielectric ◽  
Soft Matters ◽  
Synthesized Materials

Superhigh-ε materials that exhibit exceptionally high dielectric permittivity are recognized as potential candidates for a wide range of next-generation photonic and electronic devices. In general, achieving a high-ε state requires low material symmetry, as most known high-ε materials are symmetry-broken crystals. There are few reports on fluidic high-ε dielectrics. Here, we demonstrate how small molecules with high polarity, enabled by rational molecular design and machine learning analyses, enable the development of superhigh-ε fluid materials (dielectric permittivity, ε > 104) with strong second harmonic generation and macroscopic spontaneous polar ordering. The polar structures are confirmed to be identical for all the synthesized materials. Furthermore, adapting this strategy to high–molecular weight systems allows us to generalize this approach to polar polymeric materials, creating polar soft matters with spontaneous symmetry breaking.

scholarly journals Square-Planar Heteroleptic Complexes of α-Diimine-NiII-Catecholate Type: Intramolecular Ligand-to-Ligand Charge Transfer

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4622
Author(s):  
Kira I. Pashanova ◽  
Vladlena O. Bitkina ◽  
Ilya A. Yakushev ◽  
Maxim V. Arsenyev ◽  
Alexandr V. Piskunov
Keyword(s):  
Charge Transfer ◽  
Molecular Design ◽  
Crystal Packing ◽  
Molecular Geometry ◽  
Lamellar Crystal ◽  
Heteroleptic Complexes ◽  
Redox Active ◽  
Ligand Charge Transfer ◽  
Square Planar ◽  
Electron Reduction

Two heteroleptic NiII complexes combined the redox-active catecholate and 2,2′- bipyridine ligand platforms were synthesized to observe a photoinduced intramolecular ligand-to-ligand charge transfer (LL’CT, HOMOcatecholate → LUMOα-diimine). A molecular design of compound [NiII(3,6-Cat)(bipy)]∙CH3CN (1) on the base of bulky 3,6-di-tert-butyl-o-benzoquinone (3,6-DTBQ) was an annelation of the ligand with an electron donor glycol fragment, producing derivative [NiII(3,6-Catgly)(bipy)]∙CH2Cl2 (2), in order to influence the energy of LL’CT transition. A substantial longwave shift of the absorption peak was observed in the UV-Vis-NIR spectra of 2 compared with those in 1. In addition, the studied NiII derivatives demonstrated a pronounced negative solvatochromism, which was established using a broad set of solvents. The molecular geometry of both compounds can be ascribed as an insignificantly distorted square-planar type, and the π–π intermolecular stacking of the neighboring α-diimines is realized in a crystal packing. There is a lamellar crystal structure for complex 1, whereas the perpendicular T-motifs with the inter-stacks attractive π–π interactions form the packing of complex 2. The redox-active nature of ligand systems was clearly shown through the electrochemical study: a quasi-reversible one-electron reduction of 2,2′-bipyridine and two reversible successive one-electron oxidative conversations (“catecholate dianion—o-benzosemiquinonato radical anion—neutral o-benzoquinone”) were detected.

Thermodynamics of the interaction between the spike protein of severe acute respiratory syndrome- coronavirus-2 and the receptor of human angiotensin converting enzyme 2. Effects of possible ligands

2020 ◽  
Author(s):  
Cristina Garcia-Iriepa ◽  
Cecilia Hognon ◽  
Antonio Francés-Monerris ◽  
Isabel Iriepa ◽  
Tom Miclot ◽  
...  
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Molecular Mechanisms ◽  
Molecular Design ◽  
Binding Free Energy ◽  
Transmembrane Protein ◽  
Spike Protein ◽  
Converting Enzyme ◽  
Angiotensin Converting Enzyme 2 ◽  
Rational Molecular Design ◽  
Rational Evaluation

<div><p>Since the end of 2019, the coronavirus SARS-CoV-2 has caused more than 180,000 deaths all over the world, still lacking a medical treatment despite the concerns of the whole scientific community. Human Angiotensin-Converting Enzyme 2 (ACE2) was recently recognized as the transmembrane protein serving as SARS-CoV-2 entry point into cells, thus constituting the first biomolecular event leading to COVID-19 disease. Here, by means of a state-of-the-art computational approach, we propose a rational evaluation of the molecular mechanisms behind the formation of the complex and of the effects of possible ligands. Moreover, binding free energy between ACE2 and the active Receptor Binding Domain (RBD) of the SARS-CoV-2 spike protein is evaluated quantitatively, assessing the molecular mechanisms at the basis of the recognition and the ligand-induced decreased affinity. These results boost the knowledge on the molecular grounds of the SARS-CoV-2 infection and allow to suggest rationales useful for the subsequent rational molecular design to treat severe COVID-19 cases.</p></div>

scholarly journals Adherence to Ketogenic and Mediterranean Study Diets in a Crossover Trial: The Keto–Med Randomized Trial

Nutrients ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 967
Author(s):  
Matthew J. Landry ◽  
Anthony Crimarco ◽  
Dalia Perelman ◽  
Lindsay R. Durand ◽  
Christina Petlura ◽  
...  
Keyword(s):  
Randomized Trial ◽  
Randomized Clinical Trials ◽  
Secondary Analysis ◽  
Critical Factor ◽  
Detailed Examination ◽  
Diet Patterns ◽  
Time Points ◽  
Study Results ◽  
Wide Range ◽  
Diet Pattern

Adherence is a critical factor to consider when interpreting study results from randomized clinical trials (RCTs) comparing one diet to another, but it is frequently not reported by researchers. The purpose of this secondary analysis of the Keto–Med randomized trial was to provide a detailed examination and comparison of the adherence to the two study diets (Well Formulated Ketogenic Diet (WFKD) and Mediterranean Plus (Med-Plus)) under the two conditions: all food being provided (delivered) and all food being obtained by individual participants (self-provided). Diet was assessed at six time points including baseline (x1), week 4 of each phase when participants were receiving food deliveries (x2), week 12 of each phase when participants were preparing and providing food on their own (x2), and 12 weeks after participants completed both diet phases and were free to choose their own diet pattern (x1). The adherence scores for WFKD and Med-Plus were developed specifically for this study. Average adherence to the two diet patterns was very similar during both on-study time points of the intervention. Throughout the study, a wide range of adherence was observed among participants—for both diet types and during both the delivery phase and self-provided phase. Insight from this assessment of adherence may aid other researchers when answering the important question of how to improve behavioral adherence during dietary trials. This study is registered at clinicaltrials.gov NCT03810378.

scholarly journals Chalcogen Bond versus Weak Hydrogen Bond: Changing Contributions in Determining the Crystal Packing of [1,2,5]-Chalcogenadiazole-Fused Tetracyanonaphthoquinodimethanes

2021 ◽  
Vol 03 (02) ◽  
pp. 090-096
Author(s):  
Yusuke Ishigaki ◽  
Kota Asai ◽  
Takuya Shimajiri ◽  
Tomoyuki Akutagawa ◽  
Takanori Fukushima ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Density Functional ◽  
Molecular Design ◽  
Crystal Packing ◽  
Cyano Group ◽  
Density Functional Theory Calculations ◽  
Weak Hydrogen Bond ◽  
Functional Theory ◽  
Chalcogen Bond ◽  
Thiadiazole Ring

The crystal structures of a series of tetracyanonaphthoquinodimethanes fused with a selenadiazole or thiadiazole ring revealed that their molecular packing is determined mainly by two intermolecular interactions: chalcogen bond (ChB) and weak hydrogen bond (WHB). ChB between Se and a cyano group dictates the packing of selenadiazole derivatives, whereas the S-based ChB is much weaker and competes with WHB in thiadiazole analogues. This difference can be explained by different electrostatic potentials as revealed by density functional theory calculations. A proper molecular design that weakens WHB can change the contribution of ChB in determining the crystal packing of thiadiazole derivatives.

scholarly journals Engineering the Interface between Inorganic Nanoparticles and Biological Systems through Ligand Design

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1001
Author(s):  
Rui Huang ◽  
David C. Luther ◽  
Xianzhi Zhang ◽  
Aarohi Gupta ◽  
Samantha A. Tufts ◽  
...  
Keyword(s):  
Organic Synthesis ◽  
Molecular Design ◽  
Biological Systems ◽  
Ligand Design ◽  
Inorganic Nanoparticles ◽  
Organic Ligands ◽  
Biological Applications ◽  
Wide Range ◽  
Insight Into

Nanoparticles (NPs) provide multipurpose platforms for a wide range of biological applications. These applications are enabled through molecular design of surface coverages, modulating NP interactions with biosystems. In this review, we highlight approaches to functionalize nanoparticles with ”small” organic ligands (Mw < 1000), providing insight into how organic synthesis can be used to engineer NPs for nanobiology and nanomedicine.

The EU as an “enforcement patchwork”: the impact of national enforcement for compliance with EU water law in Spain and Britain

2013 ◽  
Vol 34 (2) ◽  
pp. 331-353 ◽  
Author(s):  
Mónica García Quesada
Keyword(s):  
Waste Water Treatment ◽  
National Level ◽  
State Level ◽  
Detailed Examination ◽  
Deterrent Effect ◽  
Eu Law ◽  
Wide Range ◽  
The Uk ◽  
The Impact ◽  
The Eu

AbstractFailures of compliance with European Union (EU) directives have revealed the EU as a political system capable of enacting laws in a wide range of different policy areas, but facing difficulties to ensure their actual implementation. Although the EU relies on national enforcement agencies to ensure compliance with the EU legislation, there is scarce analysis of the differential deterrent effect of national enforcement in EU law compliance. This article examines the enforcement of an EU water directive, the Urban Waste Water Treatment Directive, in Spain and the UK. It focuses on the existing national sanctions for disciplining actors in charge of complying with EU requirements, and on the actual use of punitive sanctions. The analysis shows that a more comprehensive and active disciplinary regime at the national level contributes to explain a higher degree of compliance with EU law. The article calls for a detailed examination of the national administrative and criminal sanction system for a more comprehensive understanding of the incentives and disincentives to comply with EU law at the national state level.

scholarly journals Shape memory polymer network with thermally distinct elasticity and plasticity

2016 ◽  
Vol 2 (1) ◽  
pp. e1501297 ◽  
Author(s):  
Qian Zhao ◽  
Weike Zou ◽  
Yingwu Luo ◽  
Tao Xie
Keyword(s):  
Shape Memory ◽  
Molecular Design ◽  
Shape Change ◽  
Shape Memory Polymer ◽  
Polymer Network ◽  
Stimuli Responsive ◽  
Responsive Materials ◽  
Device Applications ◽  
Temperature Ranges ◽  
Rational Molecular Design

Stimuli-responsive materials with sophisticated yet controllable shape-changing behaviors are highly desirable for real-world device applications. Among various shape-changing materials, the elastic nature of shape memory polymers allows fixation of temporary shapes that can recover on demand, whereas polymers with exchangeable bonds can undergo permanent shape change via plasticity. We integrate the elasticity and plasticity into a single polymer network. Rational molecular design allows these two opposite behaviors to be realized at different temperature ranges without any overlap. By exploring the cumulative nature of the plasticity, we demonstrate easy manipulation of highly complex shapes that is otherwise extremely challenging. The dynamic shape-changing behavior paves a new way for fabricating geometrically complex multifunctional devices.

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